1. Field of the Invention
This invention relates to the preparation of temperature sensitive II-VI semiconductors by the decomposition via photolysis or low temperature thermolysis or pyrolysis of organo-metallic compounds.
2. Description of the Prior Art
Thin metal films have been produced by conventional techniques such as vacuum deposition and electron/ion beam sputtering. These techniques are high temperature procedures and are non-selective in the materials deposited. Chemical vapor deposition using organo-metallic compounds has found increased application in the preparation of metal, semiconductor and insulating films. These deposition techniques are important in microelectronics, optoelectronics and optics.
In conventional organo-metallic chemical vapor deposition, high temperatures are used to initiate the chemical reaction near or on a substrate on which the desired film is to be deposited. Typically, elemental or compound species are used in the deposition. In the deposition of the compound species GaAs, at least two chemical species have been used, such as trimethyl gallium and arsine or trimethyl gallium and trimethyl arsenic.
The multiple source process does not always allow the simple control of the stoichiometry of the deposited film. This problem can be magnified when one of the chemical constituents is more volatile than the other such as in the deposition of HgTe. Other difficulties encountered with the high temperature pyrolysis method include thermally aided diffusion between the film and the substrate, incorporation of impurities into the film, and undesired film morphology.
One low temperature deposition technique has been described by Johnson et al., Appl. Physics Lett. 40, 798 (1982). Thin films of Zn, Se and non-stoichiometric ZnSe were produced by photodissociation of Zn(CH.sub.3).sub.2 and Se(CH.sub.3).sub.2. As in the high temperature process, stoichiometry of the film is not easily controlled.